The aim of this study was to compare paediatric patients' pain perception and behavioural response during dental injection using needle free injection (NF) or traditional injection method (TM) over two consecutive visits.

Pain is a complex and multidimensional construct that involves sensory, emotional, and cognitive processes. One of the most important part of child behaviour guidance is pain control, and the most common method used to achieve pain control in dental procedures is using local anesthetics(LA). Nevertheless, administering a LA injection is among the most anxiety-provoking procedure for both children and adults patients in dentistry. Knowledge about change in pain related behaviour during consecutive visits helps in and scheduling of treatment procedures and management of children in dental clinic .

Thus, numerious methods and techniques have been suggested to minimize/reduce pain due to infiltration of LA agents, including application of topical anesthesia , pre-cooling injection site , pressure administration to injection site , applying laser as pretreatment method , warming and buffering the local anesthetics, tactile stimulations , distraction technique, use of narrow needles and slow delivery of the injection solution, computerized injection systems , employing modern devices such VibraJect , DentalVibe, or Aculief have been tried out to allay the fears of child patients. However none of them gained universal acceptance and more situations and techniques need to be evaluated to improve stress management among patients in dental settings.

During the administration of a LA injection, an anxious patient might perceive more severe pain of longer duration than would a less anxious patient. Visually and psychologyically, the dental syringe is perceived as a threatening instrument, especially by children. Fear of pain from 'the needle' has been frequently indicated to be the most fear-evoking stimulus for dentally anxious children.

The needle- free injection system may yield a higher level of comfort, because it involves no puncture or injection phase and has emerged as a novel alternative to traditional needle- based techniques. The Comfort-inTM system (Mika Medical; Busan, Korea) is a recent dental device that uses a needle-free injection technique to administer local anesthesia. This system is a patented device using the "liquid jet" system to inject the anesthetic solution rapidly from a 0.15-mm hole with high pressure. The use of this needle-free local anaesthesia system in dentistry can be of a help in treating needle phobia patients. To the extent of investigators knowledge, there were few studies have evaluated the effectiveness of this new injection technique on primary molars in children. Investigators feel that paediatric patients are the target group for whom pain control should be adequately followed. Therefore, the current study was designed to compare paediatric patients' pain perception during dental injection using new needle-free injection system (NF) or traditional injection method (TM). In addition, secondary outcomes such as dosage of local anesthetics used (ml) and duration of the analgesia effect (min) were assessed. The expectation and tested hypotheses were that the needle-free method would produce lower pain injection and lower dosage of local anesthetics during the dental procedure.

Inclusion Criteria:

• Children with good general health without any history of allergic reactions as determined by a written history;
• Not currently taking any analgesics or sedative medication that would alter their pain perception
• Children demonstrated either 'positive' or 'definitely positive' behavior according to the Frankl Behavior Scale (FBS)
• Requiring treatment on their maxillary primary molars bilaterally with similar operative difficulties.

Exclusion Criteria:

• The existence of medical or developmental situations, history of chronic disease
• 'negative' or 'definitely negative' behavior rating according to the Frankl Behavior Scale (FBS)
• The presence of inflammation at the injection site.